Mercury Exposure: A Silent U.S. Health Crisis

Mercury Exposure: A Silent U.S. Health Crisis

Mercury toxicity, unlike many food-borne illnesses such as salmonella poisoning, doesn’t receive much attention because its symptoms are much less obvious. However, mercury is an insidious silent killer. Known as “Hg” or “quicksilver,” mercury occurs naturally within the environment. Human-induced emissions – in particular, those from coal-fired power plants that are responsible for half the world’s mercury pollution – have significantly surpassed natural sources. In fact, worldwide emissions have increased 2-5 times because of greater industrial activity during the past century. As a result, humans are now starting to understand the catastrophic consequences this poisonous element has on health, the environment and the future. According to United Nations (UN) Under-Secretary General Achim Steiner, “No one alive today is free from some level of mercury contamination; and the World Health Organization argues that there is, in the end, no safe limit.”

Public and Environmental Health

According to CAPT. Ed Rau, R.S., M.S., Environmental Officer and Special Assistant to the Director, National Institutes of Health (NIH) Environmental Protection Division, “Eating fish is the primary means of human exposure to mercury.” Bacteria and chemical reactions in an aquatic ecosystem turn this pollutant into a highly toxic organic compound known as “methylmercury.” This form is the most biologically active, thus making it particularly dangerous because it bioaccumulates in the food chain. (Bioaccumulation is the increase in an organism’s chemical concentration over time compared to the substance’s concentration in the environment.)

All animals, including humans, accrue vital nutrients such as vitamins A, D and K, trace minerals, essential fats and amino acids. However, heavy metals such as mercury can also accumulate in an organism. Once absorbed, this developmental neurotoxin is distributed primarily throughout the central nervous system (CNS) and kidneys and may result in CNS symptoms such as personality changes, irritability, fatigue, tremors, vision disturbances, ataxia, memory and concentration difficulties, and sleep disturbances. Whether these health effects occur will depend upon how much mercury an individual accumulates. Other potential health impacts include impaired thyroid and liver function and, possibly, cardiovascular problems.

According to CAPT. Sven E. Rodenbeck, U.S. Public Health Service, Agency for Toxic Substances and Disease Registry, “Women of child-bearing age are considered a high-risk group for mercury exposure because the central nervous system of a fetus is particularly sensitive to the toxic effects of mercury.” The harmful effects that may be passed from mother to fetus include brain damage, mental retardation, coordination issues, blindness, seizures and inability to speak.



This devastating effect upon the developing brain was first recognized in the 1950s in Minamata, Japan, where fish consumption with high mercury concentrations by pregnant women resulted in at least 30 cases of pediatric cerebral palsy. Rodenbeck also commented that the 2005 Centers for Disease Control’s (CDC) Third National Report on Human Exposure to Environmental Chemicals indicates that 5.7 percent of women of childbearing age in the United States had mercury blood levels within a factor of 10 of the level associated with neurodevelopmental effects.

Mercury in the Food Chain

U.S. electricity generation is a $217 billion annual business, according to the U.S. Energy Information Administration (EIA). And more than half of this electricity is produced by “dirty” coal-fired power plants. The term “dirty” was coined because one-quarter of America’s coal-burning mercury emissions are deposited within the contiguous United States, as determined by the Environmental Protection Agency. The remainder travels hundreds to thousands of miles as they adversely affect life on a global scale. Rainfall and dust deposit this pollution into ecosystems primarily within lakes and streams. Since 2000 more than three-quarters of the U.S. fish consumption advisories have resulted from methylmercury contamination, according to the U.S Geological Survey (USGS). Forty states have issued these advisories on selected water-bodies, and 13 states have had statewide advisories for some or all sportfish in rivers and lakes.

In aquatic ecosystems the toxic bioaccumulation process begins as plankton consume methylmercury in sediment. Minnows and smaller fish eat the plankton. A progression continues as larger predatory species consume smaller fish and accumulate the poisonous substance in their tissues. Concentrations increase as methylmercury moves up the food chain. Like other contaminants such as PCBs, dioxin and DDT, methylmercury is primarily stored in tissues with a high fat content. However, some is also stored in fish muscle tissue; therefore, it’s impossible to remove from fish. And, in most cases, it continues to permanently bioaccumulate in humans as well with far-reaching health problems.

Mercury can also seriously damage bird and animal health because fish are many species’ main food source. For example, loons, eagles, panthers, otters, mink, kingfishers and ospreys naturally eat large quantities of fish. Contaminated loons hatch 50 percent less young, incubate eggs for significantly less time and also produce lighter-weight eggs. Exposure has also been attributed to more limb deformities and high embryo-larval mortality among water-dwelling bullfrogs and northern leopard frogs.

Mercury and the Consumer

“Using less energy ultimately may result in fewer mercury emissions and the health effects that go with them,” explains Rau. In the 1997 assessment “Mercury Study Report to Congress,” the EPA cited this substance as an extremely hazardous air pollutant. Researchers concluded that coal-fired power plants and municipal trash incinerators were the two largest U.S. mercury emission sources and that at least 1.6 million Americans were at risk from contaminated food as a result of this pollution. However, it wasn’t until 2004 that the Food & Drug Administration (FDA) and the EPA issued a joint statement advising women of child-bearing age, as well as children, to limit their fish consumption to avoid harmful exposure.

According to Steiner: “Worldwide, vulnerable people, including pregnant mothers and babies, are warned not to eat fish such as tuna, which can contain high levels of the metal. Women of child-bearing years are advised not to eat pike, perch, burbot and eel at all; and the rest of the population, only once a week.”

“I think one of the reasons there’s confusion among the public is that there’s a lack of a comprehensive consumer advisory program,” explains Sharon Marchetti, program manager of “GotMercury?,” a campaign promoting public health education regarding mercury risks in fish and the benefits of healthier seafood choices. The FDA has established an action level of one part mercury per million in seafood. But, according to Marchetti, monitoring is not being enforced because of a tremendous increase in the global importation of food sources, particularly seafood.

Mercury- and PCB-contaminated fish are an indicator species, very much like the canary in the coalmine; and they’re sounding the warning bell. “The only method of mercury removal from fish requires reducing the release of mercury into the atmosphere. Over a considerable amount of time, the fish will accumulate less and less . . . we’re talking decades – if not a century or more,” says Marchetti.

Intentional Uses of Mercury

According to a February 2006 National Institute of Environmental Health Sciences (NIEHS) article, “Elemental Mercury Spills,” four adults melted tooth fillings to recover silver with devastating health consequences. Because fillings contain 50 percent mercury, after only one day all four developed difficulty breathing. And, despite medical care, they died within 11-24 days. In addition, the Michigan home where the fillings were melted down was so contaminated that it had to be demolished.

“One of the most harmful forms of mercury is metallic mercury vapors because this form, once inhaled, goes straight to the brain,” explains Rodenbeck. Short-term exposure to high levels may cause lung damage, nausea, vomiting, diarrhea, increased blood pressure or heart rate, skin rashes and eye irritation. At room temperature these short-term effects are infrequent; however, heating mercury increases its evaporation, which creates very high airborne concentrations and severe acute health effects. Even chronic exposure of one month or more to low levels of mercury vapor can cause nervous system and kidney damage.



The general population is exposed to mercury vapor primarily from dental amalgam. Introduced approximately 150 years ago as a tooth filling restoration, amalgam contains several metals; but mercury is the principal component (usually accounting for 50 percent). For more than 30 years concern over obvious health risks has been so heightened that the resultant debate has been known as the “amalgam wars.” As people chew, they effectively grind away the mercury filling surfaces and release mercury vapor and particles, which people breathe into their lungs or ingest. In 2008 the FDA finally agreed to classify mercury amalgam as a substance posing health risks to pregnant women, their unborn babies and children.

Mercury is also intentionally used in plastics production, paper-making, high-intensity discharge vehicle lamps, the chlor-alkali industry and gold mining. In the latter example, the metal is used to extract gold from gold-rich ore. However, the process is extremely destructive to the environment, as well as to humans and wildlife, as large quantities are released into streams and other water bodies within the U.S. and worldwide. According to Achim, “An estimated 10 million miners and their families may be suffering in countries from Brazil and Venezuela to India, Indonesia, Papua New Guinea and Zimbabwe from poisoning or exposure.”

Mercury in the Indoor Environment

Mercury in its elemental form is the silvery liquid people associate with thermometers and high school chemistry experiments. It’s also an intentionally added component in countless items ranging from light switches to laptops and from thermostats to sphygmomanometers (blood pressure instruments). According to Rau, “Usually when mercury is encased in a thermometer or a light bulb . . . , it doesn’t present any hazard. The hazard occurs when things get broken and mercury spills.”

Elemental mercury spills are a serious health threat. Anything larger than a broken thermometer or thermostat is classified as a large spill and requires clean-up action from a hazardous materials firm, the state health department or the U.S. EPA. At room temperature this mercury form evaporates slowly, thus releasing toxic vapor into the air with devastating health effects. Inhalation is a critical cause for concern as 80 percent of inhaled vapor is absorbed into the body. Some exposure through skin can occur. Chronic dermal exposure can also lead to acrodynia or “pink disease” characterized by hypersensitivity, skin rashes and discoloration, and an array of neurological symptoms. To complicate matters, spilled mercury forms small beads, which spread and make a thorough clean-up difficult.

All fluorescent light bulbs and even CFLs (compact fluorescent light bulbs) contain small mercury amounts as they cannot function without it. However, while a fever thermometer may contain as much as a gram of mercury, a CFL bulb contains only a few milligrams. By comparison CFLs are four times more efficient, release four times less mercury into the environment than an incandescent bulb and average 90 percent less in total operating cost over their lifetime.

Rau explains: “You have to keep the risk in perspective. The amount in CFLs is tiny compared to other things we commonly have in our indoor environment. What’s also not understood is that CFL use actually has a very beneficial effect in reducing mercury contamination in the environment.” CFLs reduce electricity use and, as a byproduct, the mercury release from power plants. When recycled properly, CFLs have negligible impacts on the environment. However, improper disposal via municipal waste incineration or landfills does present a risk of release to the environment.

Elemental mercury exposure in schools occurs accidentally from broken thermometers and thermostats, and spills from improperly stored or handled mercury in the chemistry lab. In 2004 six EPA regional offices responded to mercury spills that included 12 school emergency clean-ups with costs ranging from $1,000-$200,000. Another indoor form of mercury exposure results from rituals. In January 1993 the EPA’s Office of Pollution Prevention and Toxics (OPPT) investigated religious supply companies, candle shops and folk pharmacies or botánicas to find they commonly sold mercury candles as well as liquid mercury vials to be burned in candles, sprinkled around rooms or consumed as a home remedy.

Got Mercury?

The long-term implications of mercury contamination are unknown at this time, particularly with respect to a generation of innocent children who may have been inadvertently exposed before birth. According to an NIEHS analysis using data from the Centers for Disease Control and Prevention (CDC), between 136,588 and 637,233 children each year have cord blood mercury levels associated with lower IQs. This lost intelligence causes diminished economic productivity over a child’s lifetime.



This lost productivity is the major economic cost of methylmercury toxicity, which approximates $8.7 billion annually. Such expenses will continue to grow until mercury emissions are regulated effectively.

Rau advises: “Reducing mercury is really something that we’re not doing for this generation; we need to do it for the next generation. Not considering the health implications and the impacts on our children, just from an economic standpoint, if the impact is anywhere near the order of magnitude approximated, it more than justifies controlling mercury emissions. As with emissions, the easiest solution is prevention. It’s certainly much easier to prevent spills than to clean them up. It’s much better to have healthy children than it is trying to treat them.” Achim concurs, “We estimate that every kilogramme of mercury taken out of the environment can trigger up to $12,500 worth of social, environmental and human health benefits.”

With this in mind, has developed the “Got Mercury?” calculator based on FDA protocol and guidelines for fish consumption. This calculator allows a consumer to insert body weight, type of fish species and amount desired; then it determines the mercury consumption level. “It’s really important that consumers ask for this information and that they remain their own personal health advocates,” says Marchetti.

In addition, according to Rodenbeck, tests are available for the general public to measure blood mercury levels. He states, “If a person is concerned that they may have been exposed to mercury, they can go to their local health clinic and have samples taken for testing.” Blood or urine samples are used to test for metallic mercury exposure and for inorganic mercury forms while mercury in whole blood or in scalp hair is measured to determine exposure to methylmercury.

A Low Mercury Future

In the mid-1990s the NIH began a voluntary initiative to eliminate mercury use in medical applications at its Warren G. Magnuson Clinical Center. By 2001 the initiative had been expanded into a more organized, agency-wide campaign covering 5,000 laboratories and other non-clinical areas in all NIH installations within the United States. Today the “Mad as a Hatter? Mercury-Free Campaign” seeks to eliminate all unnecessary mercury uses in NIH facilities, to encourage use of safer alternatives in biomedical research, to increase general awareness of mercury hazards and to prevent mercury spills and pollution. The campaign has now been adopted by many other organizations in the U.S. and internationally.

“Overall it’s an attempt to reduce potential for exposure. Unfortunately, we still have situations with mercury spills occurring in schools, homes and healthcare facilities; and just about all of the mercury uses in these places are unnecessary at this point. We still have mercury used in our indoor environment because there just isn’t enough awareness of where mercury is found and how to replace it,” explains Rau, who received the American Chemical Society’s Howard Fawcett Award in 2005 for his “Mad as a Hatter? Mercury-Free Campaign” efforts.

Rau continues: “The sources of mercury from human activities are steadily increasing as the population increases and as more power plants are being built around the world. It’s unlikely that, no matter what strategy we use, there will be a significant decrease in emissions for some time . . . so we’re going to have to live in an environment where there’s some level of mercury contamination. This provides a very good example of how the different sustainability initiatives – be it energy use reduction, water conservation, less use of toxic materials – all tie back to health. Sustainability relates directly to health.”

Achim believes that “flexibility needs to be shown. But only by setting a clear and unequivocal landscape of a low mercury future will governments trigger innovation and alternative products and processes . . . Prevarication and inaction over the global mercury challenge, however, is no longer an option. We owe it to anyone who has an interest in a healthier, less-polluted world.”